Process of improving the magnetic qualities or iron-silicon-manganese alloys.



v TED STATES PATENT OFFICE.

ROBERT ABBOTT HADFIELD, OF SHEFFIELD, ENGLAND. PROCESS .OF IMPROVING TIIE MAGNETIC QUALITIES 0F IRON-SILICON-MANGANESE ALLOYS.

Patented necf4. 1906.

Application filed August 21, 1906. serial No. 331,423.

To all whont it may concern: I

Be it known that 1, ROBERT ABBOTT HAD- F ELD,a subject of the King of Great Britain, and a resident of Sheflield, England, have-invented a certain new and useful Improvement in Processes of Improving the Magnetic Qualities of Iron-Silicon-Manganese Alloys,

of which the following is a specification.

In another application for Letters Patent, Serial No. 324,892, filed July 5, 1906, I have described and claimed an alloy of iron with silicon in such proportion as to increase the magnetic permeability and electric resistance and to decrease the hysteresis action, and thus to reduce the total magnetic and electric losses in the mixture, (when such alloy is used for ballast-coils, transformer plates, or like electric apparatus to which aloy manganese is added in order to improve the physical properties of said alloy in oint of capacity for being worked, rolle or forged. In order to effect the best reduction of the said magnetic and electric losses, a heat treatment of said alloy is necessary.

My present invention is a process of heat treatment applied to the aforesaid iron-silicon-manganese alloy for the purposestated.

In carrying my invention into efiect Ifirst prepare an alloy of iron and silicon inmolten state and add manganese thereto in proportion not exceeding one-half of one per cent. of the total mass. Such a proportion of manganese is not sufficient to im air the ma netic qualities of the alloy, while it is su cient materially to improve its working or rolling ualities. I then cast the ingots in the usua way and convert the ingots into desired shapes and thicknesses and heat the alloy to a tem erature above a critical point (hereinafter efined) and then cool the same slowly.

When said alloy is subjected to progressive temperature variations (below fusion) from 600 centigrade upward, it undergoes at a certain temperature-point an apparent molecular change, and on further alteration of tem erature another point ensues at which anot or molecular change occurs.

The term critical point herein used means the point ofhigher temperature of the two above noted and approximates to the 900-centigrade point in the case of pure iron, which is the lower limit of its so-called gamma state. This gamma state is definitely shown, for example, in ordinary carbon steels when heated. A diagram accurately illustrating this oint is given by Messrs. Arnold and McWi liam in their paper on the thermal transformations of carbon steels published in the J oumal of the Iron and Steel Institute, 1905, Vol. 2. Diagram 2 in this paper shows the critical point for a certain carbon steel at about 870- centigrade. The alloy should be low in carbon and contain, say, under twelve one-hundredths of one per cent.

For certain purposes, 1f desired, the material ascast may be used, being suitably treat-- ed in the same manner as the forged or rolled material.

I claim- 1. The process of increasing the magnetic permeability and electric resistance and reducing the hysteresis action of an iron-silicon-manganese alloy low in carbon, which consists in heating said alloy to a temperature above its critical point, and then cooling.

2. The process of increasing the magnetic permeability and electric resistance and reducing the hysteresis action and also of improving the working and rolling qualities. of an iron-silicon alloy, low in carbon, which consists in melting together iron and silicon, adding manganese in proportion not suffi cient to impair said magnetic qualities casting into in ot form converting said ingots into desire shapes and thicknesses by appropriate means, heating said alloy to a tem-- ROBERT ABBOTT HADEIELD.

Witnesses:

WILLIAM CRoss, WILLIAM OBAWLEY. 

